Circuit elements especially for use as scanning coils



E. W. BULL Sept. 9, 1969 CIRCUIT ELEMENTS ESPECIALLY FOR USE AS SCANNINGCOILS Filed July 20, 1966 llllall FIGS FIG.2

FIGZI United States Patent U.S. Cl. 335-213 Claims ABSTRACT OF THEDISCLOSURE A circuit element which comprises a tape like structure whichis intended to be rolled into a cylindrical or like form to constitute ascanning coil assembly for a cathode ray tube has conductive patterns oneach side thereof comprising longitudinally extending substantiallyrectangular waveforms the two patterns being staggered with respect toeach other.

This invention relates to circuit elements especially for use asscanning coils such as may be used for deflecting electron beams incathode ray tubes, and especially to such coils for use with vidiconcamera tubes.

Saddle type coils are frequently used to produce line and fielddeflection in cathode ray tubes and if such coils are to be manufacturedinl arge numbers with consistant performance it is desirable that theyshould be produced by printed circuit techniques.

It is an object of the present invention to produce an improved circuitelement which can serve as a printed circuit scanning coil.

According to the invention there is provided a coil comprising aflexible base which is rolled and which supports two overlapping andmutually insulated electrically conductive patterns each patterncomprising a repetitive circumferentially continuous waveform includingcircumferential parts and alternate parts transverse thereto meetingeach other at right angles, one pattern being displaced relative to theother so that the circumferential parts of the respective Waveforms arestaggered so that the coil as rolled is equivalent to two diametricallyopposed scanning coils wherein the parts transverse to thecircumferential parts extend parallel to and longitudinally of the coilsurface. The pattern which extends circumferentially when the base isrolled, would extend longitudinally if the base be unrolled.

It will be appreciated that said base may comprise two layers ofinsulating material overlapping each other, each supporting a conductivepattern and assembled to form a unit. Alternatively the two patterns maybe provided on the outer surfaces of a sheet of insulating material.

According to another aspect of the invention there is provided a coilcomprising a base rolled to conform to a surface of revolution andsupporting two overlapping and mutually insulated electricallyconductive patterns, each pattern comprising a repetitivecircumferentially extending rectangular waveform, one pattern beingdisplaced relative to the other so that the circumferential parts of therespective waveforms are staggered. The pattern which extendscircumferentially when the base is rolled, would extend longitudinallyif the base be unrolled.

In order that the invention may be clearly understood and readilycarried into effect, it will now be described by way of example withreference to the accompanying drawings, in which:

FIGURE 1 shows the upper side of a circuit element according to theinvention,

FIGURE 2 shows the printed pattern on the underside 3,466,580 PatentedSept. 9, 1969 ice of said circuit element shown in FIGURE 1, but viewedfrom the upper side,

FIGURE 3 shows the combination of FIGURES 1 and 2, and

FIGURE 4 shows a scanning coil according to the invention mounted on avidicon camera tube.

Referring to FIGURE 1, a base in the form of a strip of flexibleinsulating material 1 has side-by-side con tinuous conductors 2 printedon each of its major surfaces. Each conductor has alternate longitudinaland transverse parts, corresponding parts of adjacent conductors beingparallel so that each conductor conforms to a pattern comprising arepetitive longitudinally extending rectangular waveform in which thealternate longitudinal and transverse parts are at right angles to eachother. For the sake of simplicity in the drawing only three conductorsare shown, although in practice a larger number may be required. Forexample in a coil for line deflection ten side-by-side conductors havebeen found suitable, and for field deflection twenty sideby-sideconductors have been found suitable. The strip is sufliciently long toaccommodate several cycles of the square-wave, for example it has beenfound that with the above-mentioned number of conductors four cycles aresuitable for line deflection and eight cycles for field deflection.Furthermore, although as shown the conductors occupy little spacecompared with the space between them, this is to clarify the drawing,and in practice the conductors may be 0.1 in. wide and the space betweenthem only 0.0-1 in.

FIGURE 2 shows the pattern of conductors which is laid down on theundersurface of the strip shown in FIG- URE 1, but as seen from theupperside. The number, spacing and pattern of conductors is similar tothat on the upper surface.

FIGURE 3 illustrates the complete strip with the conductors on the uppersurface as in FIGURE 1 shown in unbroken lines and the conductors on theunderside as in FIGURE 2 shown in dashed lines. The conductors on theupper and under surfaces are electrically connected by throughconnectors indicated at 3, and connections provided for terminals forthe coils as indicated at 4. The pattern on the two surfaces of the base1, though mutually insulated by the base, are connected together by theconnectors 3 to form a single series circuit in which the direction ofcurrent flow, for a particular polarity of supply voltage, is indicatedby the arrow heads shown on the conductors. The two patterns providedrespectively on the surfaces of the base 1 are superimposed butdisplaced longitudinally one relative to the other so that, whereastransverse parts of the two waveforms are in register, the longitudinalparts are staggered. The two conductive patterns therefore form a numberof virtual elementary coils each of which will produce a magnetic fieldperpendicular to the plane of the insulating base 1, the magnetic fieldshaving alternately opposite senses.

In use the strip as described is rolled as shown in FIGURE 4 round thevidicon tube to form a cylinder, similar parts of the square waveoverlapping. For example the lines marked X and Y on the figuresoverlap, the distance between X and Y representing the circumference ofthe cylinder. As is clear, the patterns are such that successive cyclesof each waveform subtend the same angle at the axis of the cylinder. Theparts of the conductive patterns which were transverse before rollingthe base 1 to conform to a cylindrical surface now become parallel tothe cylinder axis and form two diametrically opposite axially extendinggroups of conductors which are the active turns of two virtual saddletype coils. In other words the cylinder or cylindrical surface to whichthe rolled strip now conforms is of such diameter that alternatetransverse parts of the conductors on each surface of the strip aresubstantially diametrically opposite.

The staggered parts of the printed conductors which were longitudinalbefore rolling now extend circumferentially and constitute the end turnsof the coils. Leads 6 are connected to the terminals 4 on said strip.Insulation must be provided to prevent overlapping conductors fromcontacting, and this is provided either by coating the printed circuitwith an insulating layer before rolling or by interleaving a separatestrip of insulating material in the strip as it is rolled.

It is to be noted that in practice the scale of the patternlongitudinally will generally require to increase gradually along thestrip to take account of the increasing diameter of the cyinder as thestrip is rolled to fit round the tube to ensure that similar parts ofthe conductor waveform continue to register. The parts of the conductorswhich are longitudinal when the base 1 is flat need not be spaced, orneed not all be spaced, to register exactly on rolling the base. Thelongitudinal spacing of the transverse parts of the patterns may beselected to provide a graded distribution of the axially extendedconductors or to increase the angle subtended by the active conductors,when the pattern is rolled.

Locating holes may be provided along the strip so that with their aidthe strip may be rolled with the required accuracy of registration ofthe conductors over each other.

The spacing of the conductors and their precise location may be adjustedto produce desired field patterns.

It will be appreciated that if the circuit element is intended to beused to provide scanning coils which fit round the conical portion of acathode ray tube instead of a cylindrical portion as described above,the flexible base insulating material will be required to differ inshape from that illustrated. It will have the shape of an annularsector, and the rectangular waveform will have to be curved to followthe curvature of said strip. The term longitudinally continuousrectangular waveform used in the specification and claims is intended todescribe such a waveform as well as the straight form shown in thefigures.

A single strip may have two distinct sets of conductors printed on it,one for line deflection and the other for field deflection, so that bothsets of scanning coils for a cathode ray tube may be constructed byrolling a single strip. Furthermore, if electrostatic screens arerequired between the tube and coils and/or between the two sets of coilsthese may be printed on the strip and the assembly for the tube againstproduced by a single rolling operation.

Therefore, from one aspect, the invention provides a circuit elementwhich comprises a thin, flexible, elongated insulating member supportingoverlapping conductive patterns on its two outer surface areas. Eachpattern comprises a plurality of side-by-side conductors each conformingto a substantially rectangular waveform consisting of alternatelongitudinal and transverse parts at right angles to each other with thelongitudinal parts of the rectangular waveform on one surface beingstaggered with respect to the longitudinal parts of the rectangularwaveform on the other surface. Further, means are provided connectingthe ends of said conductors successively to one another to connect saidconductors in a single series circuit, so that the current in thetransverse parts of the plurality of conductors on one surface flows inthe same direction as the current in the nearest transverse parts of theconductors on the other surface.

The base need not be composed entirely of insulating material or of asingle strip. It may for example consist of more than one layer ofinsulating material. Moreover although the invention has been describedin relation to coils for a television or like pick-up tube, it isapplicable to cathode ray image reproducing tubes and the like. Further,the invention is not restricted in its application to scanning coils butmay be applied to the formation of resolver coils, motor coils and thelike.

What I claim is:

1. A circuit element comprising a flexible base which supports twooverlapping and mutually insulated electrically conductive patterns,each pattern comprising a repetitive longitudinally continuoussubstantially rectangular waveform consisting of alternate longitudinaland transverse parts at right angles to each other, one pattern beingdisplaced relative to the other so that the longitudinal parts of therespective waveforms are staggered so that the base can be rolled insuch a way as to cause the patterns to form the equivalent of twodiametrically opposed scanning coils wherein the transverse parts becomeparallel to the coil axisand the longitudinal parts extendcircumferentially of the coils.

2. A circuit element according to claim 1 in which said patterns areadherent respectively on two surfaces of flexible insulating sheetmaterial forming said base.

3. A circuit element according to claim 2 in which said patterns areadherent on the outer surfaces of a flexible insulating sheet.

4. A circuit element according to claim 1 in which each pattern includesa plurality of side-by-side conductors each of which conforms to therespective longitudinal waveform.

5. A circuit element according toclaim 1 in which the patterns areelectrically connected together to form a single series circuit, so thatthe current in each transverse part of one waveform flows in the samedirection as a current in the nearest transverse part of the otherWaveform.

6. A circuit element according to claim 1 in which said patterns aresuch that successive cycles of each waveform subtend the same angle atthe axis of the coil surface.

7. A coil comprising a flexible base which is rolled and which supportstwo overlapping and mutually insulated electrically conductive patternseach pattern comprising a repetitive circumferentially continuouswaveform including circumferential parts and alternate parts transversethereto meeting each other at right angles, one pattern being displacedrelative to the other so that the circumferential parts of therespective waveforms are staggered so that the coil as rolled isequivalent to two diametrically opposed scanning coils wherein the partstransverse to the circumferential parts extend parallel to andlongitudinally of the coil surface.

8. A coil comprising a flexible base which is rolled and which supportstwo overlapping and mutually insulated electrically conductive patternseach pattern comprising a repetitive circumferentially continuousrectangular waveform including circumferential parts and alternate partstransverse thereto meeting each other at right angles, one pattern beingdisplaced relative to the other so that the circumferential parts of therespective waveforms are staggered so that the coil as rolled isequivalent to two diametrically opposed scanning coils wherein the partstransverse to the circumferential parts extend parallel to andlongitudinally of the coil surface.

9. A circuit element comprising:

(a) a thin, flexible, elongated insulating member supporting mutuallyinsulated overlapping conductive patterns on two surface areas,

(b) each pattern comprising a plurality of side-by-side conductors eachconforming to a substantially rectangular waveform consisting ofalternate longitudinal parts and transverse parts at right angels toeach other,

(c) the longitudinal parts of the rectangular waveform on one surfacearea being staggered with respect to the longitudinal parts of therectangular waveform on the other surface area,

((1) means-connecting the ends of said conductors successively one toanother to connect said conductors in a single series circuit, so thatthe current in the transverse parts of the plurality of conductors onone surface area flows in the same direction as the current in thenearest transverse parts of the conductors on the other surface area.

10. A circuit element according to claim 9 in which said flexibleinsulating member is rolled to conform to a cylindrical surface whereinthe transverse parts become parallel to the axis of such cylindricalsurface and the longitudinal parts extend circumferentially of suchcylindrical surface and said cylindrical surface being of such diameterthat alternate transverse parts of the conductors on each surface areaof the member are substantially diametrically opposite,

References Cited UNITED STATES PATENTS 2,831,136 4/1958 Hanlet 335299 XR3,011,247 12/1961 Hanlet 336--200 XR 3,080,541 3/1963 Parker 336200BERNARD A. GILHEANY, Primary Examiner US. Cl. X.R.

